U.S. Rep. Ann Wagner won’t pursue a run against U.S. Sen. Claire McCaskill in 2018, a move that likely clears the way for Missouri Attorney General Josh Hawley to enter the race.

Wagner, a Republican from the St. Louis area and former state party chairwoman, had been seen as the early frontrunner to take on McCaskill, the Democratic incumbent, after raising nearly $1 million during the first three months of 2017. The race, which could determine control of the U.S. Senate, is expected to be one of the most expensive and hotly contested of 2018.

However, Wagner, a former ambassador to Luxembourg, announced her decision Monday to seek re-election to the U.S. House instead of pursuing a run for Senate.

“Those who know me well know I put my family and my community first. While I am grateful for the incredible support and encouragement I have received from across Missouri to run for United States Senate, I am announcing today my intention to run for re-election to the United States House of Representatives in 2018,” Wagner said in a statement.

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“The 2nd District is my home. It’s where I grew up, went to school, have worked and volunteered, raised my kids, and attend church every week — there is no greater honor than representing a place and people that I love,” she continued.

“I’ve known him since he was a law student…and I think he is a once-in-a-generation type person,” Danforth, a Republican who represented Missouri for nearly two decades, said last week before Wagner announced her plans.

“He’s obviously an excellent vote-getter because he led our ticket in the last election, but beyond that I think he adds a great deal to politics and to government by his presence in it,” Danforth said, citing Hawley’s background as a law professor.

Danforth compared Hawley to Daniel Patrick Moynihan, a New York Democrat who spent 24 years in the Senate after serving a variety of roles in the Kennedy, Johnson and Nixon administrations. Moynihan, who passed away in 2003, was succeeded by Hillary Clinton in 2001.

“He deepened our thinking about government and about public policy and I think Josh has that same capability. He’s equally bright as Pat,” Danforth said.

Hawley, who was elected to his first term as attorney general in November, said last month that it was “awfully early” to discuss a run for Senate. On Monday, he did not say whether he has gotten closer to a decision about a run. He instead offered his praise for Wagner.

“Ann is a tough fighter for Missouri and she would have mounted a strong conservative challenge to Senator McCaskill. Josh values Rep. Wagner’s help fighting human trafficking and federal over-reach,” Scott Paradise, Hawley’s political spokesman, said in a statement.

McCaskill’s campaign shrugged at the news.

“One politician has taken a pass, we're sure another politician will take her place,” said John LaBombard, McCaskill’s spokesman.

Other Republican candidates are also contemplating campaigns. U.S. Rep. Vicky Hartzler, a Republican whose district covers western Missouri, has not ruled out a run, according an aide.

Wagner’s campaign did not immediately comment on whether the effort to recruit Hawley to the Senate race played a role in her decision.

Former U.S. Ambassador to Belgium and St. Louis businessman Sam Fox sent a letter to GOP donors last week asking them to hold off on supporting other candidates until Hawley made a decision about the race.

Missouri Democrats were already preparing for Hawley as a potential candidate prior to Wagner’s announcement.

“Just six months into his new job, Josh Hawley is already looking for the next campaign — all while ignoring his promises, like his pledge to create an anti-corruption unit, or clean up Jefferson City’s corruption,” Stephen Webber, the chairman of the Missouri Democratic Party, said in an email last week. “It seems he’s more busy looking up the ladder, than looking out for Missouri.”

Lindsay Wise of McClatchy’s Washington Bureau contributed to this report.